1. Field of Invention
This invention pertains to a fabricated interconnect device for coupling between open ends of the vascular or arterial flow line within a human circulatory system. More particularly, the present invention relates to an interconnect device for enabling implantation of a total artificial heart, ventricular assist device or for similar applications wherein the arterial or vascular network of the body must be repaired or modified to redirect blood flow.
2. Prior Art
Modern medicine has developed many procedures and devices relating to treatment and care of patients with disorders of the circulatory system. Frequently, treatment procedures require the physician to interrupt the natural vascular or arterial network by inserting replacement valves, shunting devices and other prosthetics within the flow line of the circulatory system. Representative examples of such treatment procedures include the use of aortic and arterial-venus shunting, bypass and cardiac assist devices, and more recently, the total artificial heart. It is perhaps in this last area of heart implantation that the acute risks of modifying or interferring with blood flow in the circulatory system are most evident. Without exception to date, each patient having a permanent total artificial heart implant has succumbed to the affects of thrombogenesis and thromboembolism. These difficulties have also been the focus of research in an effort to develop a successful clinical program utilizing the total artificial heart as a bridge to later cardiac transplantation.
During the time that a patient's life is dependent upon the artificial heart, he is subject to an extreme high risk of thrombogenesis or thrombus formation. These emboli break free from their point of origin and frequently travel to the brain resulting in thromboembolism and the attendant effects of stroke. In view of this high risk, clinical practice attempts to minimize support time on the artificial heart to the shortest possible period because of the potential for stroke and attendant brain damage. Even use of the artificial heart in experimental animals has revealed that thrombus formation is a common observation for current devices even for short implant periods.
Successful implacement of the artificial heart requires quick attachment of the device to the left and right atria, aorta and pulmonary arteries. The attachment procedures are very difficult because of the restricted space and visual impairment resulting from excessive flow of blood. Consequently, the dominant devices for attaching the arteries to the artificial heart have been quick connect valves such as are illustrated in FIG. 1. This system relies on a polyurethane graft or cuff for developing a total seal on a rigid valve-holding ring 11 which includes a lip 12 adapting the cuff 10 for snap-in-place attachment. The cuff is modified with an attachment flange 13 which includes a shoulder designed to snap in place over the lip 12 to secure the cuff 10 and valve-holding ring together. The holding ring 11 includes a movable valve element 14 which is secured to a valve support ring 15. The valve support ring 15 is sandwiched between a retaining shoulder 16 of the holding ring 11 and an high durometer plastic holding ring 17 which includes a retaining shoulder 18 for securing the valve support ring 15 in place. The artificial heart body or BIOMER .TM. (a polyethlene polyurethane assigned to Ethicon, New Brunswick NJ) housing 19 is adhesively coupled to the ISOPLAST .TM. (a polyethylene polyurethane assigned to Dow Chemical Co., Inc.) valve holding ring 17.
Prior to inserting the high durometer plastic valve holding ring 17 into its companion valve-holding ring 11, the metallic support ring 15 is inserted within the plastic ring 17 as shown in FIG. 1. This combination is then inserted or screwed into the receiving channel 20 formed in the valve-holding ring 11. Sealing contact at shoulder 16 by the adjacent side edge of the valve support ring 15 is based on contact arising from the pressure applied when inserting this plastic ring and attached support ring in interlocking position.
A major cause of thrombogenesis within this valve arrangement are small gaps which occur between the metallic support ring 15 and shoulder face 16. Similar thrombus formation regularly occurs at the opposite contacting side of the metallic support ring 15 on shoulder 18. In addition, thrombogenesis is also common at the quick connect junction 21 between the arterial cuff 10 and rigid valve housing 11. Gaps in this region arise because of fatigue which reduces tension at the quick connect site, as well as imperfections in construction of the BIOMER-coated cuff 10 and nonuniform forces applied by the surrounding organs and tissue of the body. Those skilled in the art of solution casting for soft polyurethanes are well aware of the difficulty of structuring a fabricated body with uniform strength and elasticity along all directions. The resultant occurrence of shrinkage or imbalance of thickness due to viscosity differences contributes to gap formation when coupled to the rigid plastic valve housing 11. It is also well known that the polyurethane body has a tendency to creep or shift position which can lead to unexpected stresses around the quick-connect location. In addition, nonuniform response to temperature can result in gap formation at the quick-connect location.
The quick-connect device illustrated in FIG. 1 also presents difficulties for the surgeon during implantation. Because of the presence of fluids and impaired observation due to blood flow, the surgeon must rely upon his sense of feel to detect proper positioning of the cuff 10 at the quick couple location. If the cuff is inserted too far or if the cuff fails to be properly set in place, gap formation is likely and thrombosis will be the natural result. If the physician snaps the cuff in place in an incorrect orientation, a tool is required to release the quick connect configuration. Use of this tool may result in local fatigue where the soft plastic is pried apart from the shoulder 12. This quick-connect configuration also limits the surgeon's ability to freely rotate the valve housing so that optimum positioning can take place for the artificial heart. The combination of these problems creates a complex challenge for the surgeon, who is already severely limited in time and working space.